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Saturday, January 17, 2009

Perigean moon above the woods of Castilla

As usual, I was driving my car from Madrid to Segovia county taking my girlfriend home. Saturday and Sunday night were two fantastic full moon nights and we stopped our car at the Alto del León to observe the beauty of our satellite. Maybe it was the perfectly clear atmosphere, maybe it was the complete absence of other light sources, maybe it was just the magic of the moment, but the moon seemed really different, that night. Rarely I did see such a big and bright moon! When we stopped the car, the trees in the wood at night were casting shadows as if it were the evening. Impressive.

This morning I remembered the phenomenon and had a rapid check just to confirm the obvious: it was a perigean moon. As you (should) remember when you studied the Kerpler's laws of planetary motion, the orbit of a planet is an ellipsis with the sun at the focus. In the earth-moon problem, the moon's orbit is an ellipsis with the earth at the focus. Now, if you remember what an ellipsis is, it's clear that there exist two points in the orbit, called perigee and apogee, in which the distance earth-moon is, respectively, minimum and maximum.

Long story short: what we were observing Saturday night was a full moon at his perigee. Approximately 15% bigger and brighter! I think it was my first perigean moon and, moreover, I enjoyed it with the best company!